The present invention is directed to non-intrusively measuring the time for the full stroke operation of a pneumatically controlled valve, and more particularly, to measuring the time interval for an electrically actuated, pneumatically controlled valve to fully open or close in a nuclear facility.
Pneumatically controlled valves are used extensively in nuclear power generating plants. The time interval for individual valves to open or close is very important for many safety aspects of nuclear plant operation. Valves need to fully operate within set parameters to ensure that safety regulations are being met. To date the timing of valves has been accomplished by hand held stop watches and technicians in different locations communicating by phone. One technician will start the valve closing or opening sequence from the control room while another technician observes the valve operation and performs the timing by hand. Other methods include observing indicator lights which may or may not be properly set up or functioning.
There are many disadvantages to the present methods of timing valves. In both cases, observation of the valve per se or observation of the indicator lights, there is the human variable of when the timing begins and ends. Not only can the timing be inaccurate, but because of variations in the human hand and eye between individuals and even between the same individual from day to day, the degree of inaccuracy will be inconsistent. Thus, it can be difficult to accurately identify valve degradation over a period of months or years by comparing valve timings. Also in cases where the timing is performed by actually observing the valve start and stop, there is no accurate compensation for the time elapsed for the operation of the pneumatic control mechanism.
At present there are methods available for testing valve operation in the plant. Use of such methods, however, would require disconnecting the valve control mechanism from the control room. A signal would be generated from the test equipment to cause valve actuation. Timing could then be performed from various test sights on the valve. This method of valve testing is unacceptable for safety testing the operation of valves in many nuclear power plants. The valve needs to perform in the same environment and situation it would need to perform in if an actual emergency were to occur. The disconnection and then reconnection of safety related signal and/or control lines presents licensing problems.